This invention relates to a sintered oil impregnated bearing and its manufacturing method, especially, a sintered oil impregnated bearing having superior frictional characteristics, and its manufacturing method.
Formed from a porous-type sintered alloy, and after being impregnated with oil, such sintered oil impregnated bearings can be used for extended periods of time without lubrication, therefore, they are widely used as bearings for rotating shafts of various machines.
This type of sintered oil impregnated bearing is constructed, as illustrated in FIG. 6, which shows a bearing hole 2 formed in a bearing main body 1 made of a porous-type sintered alloy, a rotating shaft of a smaller diameter than the hole 2 is inserted in the hole, and the lubricating oil drawn off from a large number of oil-containing holes (pores) in the bearing main body 1 due to the pumping action caused by the rotation of the rotating shaft 3, and the lubricating oil seeping out due to expansion caused by frictional heat form an oil film on the sliding face 4 of the bearing hole 2, thereby freely rotatably supporting the rotating shaft 3.
However, in the above noted sintered oil impregnated bearing, because there are a large number of pores formed on the sliding face 4 of the bearing hole 2 on which the rotating shaft 3 is sliding, even if the oil film is generated, a part of the lubricating oil leaks from the above noted pores causing a drop in the oil pressure, and as a result, local touching of the rotating shaft 3 with the sliding face 4 takes place. When such local touching occurs, the coefficient of friction of the oil impregnated bearing becomes large, and burning is easy to be generated, and this was a fault. Therefore, the present inventors considered that if the lubricating oil can be made not to leak out from the sliding face 4, a strong oil film without having an oil pressure drop can be formed, thus enabling the lowering of the coefficient of friction of the bearing.